Treatment of hydrocarbon oils



April 6, 1937- G. ARMISTEAD, JR 2,076,394

TREATMENT OF HYDROCARBON OILS Filed NOV. 2l, 1929 Patented Apr. 6, 1937PATENT OFFICE.

TREATMENT or maconlinux oms George Armistead, Jr., Port Arthur, Tex.,signor to The Texas Company, New York, N. Y., a corporation of DelawareApplication November 21, 1929, Serial No. 408,704 a claim. (c1. 1st-9s)This invention relates to the production of distillate oils and hasparticular application in the production of such distillate oils asgasoline or motor fuel and the like.

In general, the invention contemplates a process in which distillateoils, such for example as cracked distillates obtained from crackingprocesses, are subjected to distillation and iractionation by bringingthem in contact with the heat of vapors obtained in distilling residuederived from the cracking process. Thus, for example, hydrocarbon oilmay be subjected to cracking and a distillate, such as a gasoline ornaphtha distillate, and tar or residue, obtained from the products ofcracking. The tar or residue may be subjected to vaporization by meansof its contained heat at reduced pressure and the evolved vaporssubjected to fractionation in a fractionating tower while distillateobtained from the cracking process is introduced as a reux into thetower to thus supply cooling to the tower and for vaporizing thedistillate to the extent desired, a vapor fraction of desired end pointcomprising vaporized constituents of the cracked distillate as well asany vapors of desired boiling point obtained in the distillation of theresidue being taken off the tower and collected as a condensate.

Experiments have shown that in cracking hydrocarbon oils by distillationunder superatmcspheric pressure a greater yield of gasoline or otherlight distillate of given end point can be most economically obtained,so far as the cracking still, a distillate having a higher end pointthan dephlegmator or fractionating tower, employed in fractionating thevapors from the cracking that of the given end point gasoline desired.Thus for example, assuming that it is desired to obtain a 400 F. endpoint gasoline, if a distillate of for example 450 F. to 500 F. be takenoff the pressure fractionating tower a greater amount of 400 F. endpoint gasoline will be produced by the apparatus than would be the caseif distillate of 400 F. end point were taken oiT. The reason for this isthat the higher end point distillate taken oil? as a vapor from thetower requires a higher temperature inthe top of the tower than in thecase of the lower end point distillate; the higher temperature at thetop of the tower requires a correspondingly higher temperature in thestill or reaction .chamber which increases the cracking rate in thestill and thus results in increased cracking and yield of gasoline. Ifit is sought to obtain this increased yield without increasing the endpoint ot the pressure distillate it is necessary to apply more coolingto the tower to hold the end point down which results in an increasedquantity of heat being consumed in vaporizing the greater quantity ofreilux supplied to the tower and consequently an increased production inthe tower of reflux condensate to be returned to the cracking zone,thereby causing an increase in fuel ccnsumption that makes it impossibleto increase the yield in this way as economically as by lncreasing theend point of the pressure distillate. When taking oil? the higher endpoint distillate it is necessary, however, to redistill and iractionatethis distillate in order to obtain the lower end point product desiredand the cost oi this operation has hitherto negatived the advantageobtained in the cracking operation of obtaining the maximum yield offractions of desired boiling point.

According to my invention the production of maximum quantities o!gasoline or other distillate desired may be obtained by taking off fromthe pressure fractionating tower a distillate having a higher end pointthan that desired for the iinal product and, by directing thisdistillate as a reilux into a tower employed in fractionating vaporsevolved in the auto distillation of the pressure tar or residue, thedistillate may be vaporized to the extent desired to form a finalproduct of the desired end point. In this way the maximum production oigasoline or light distillate of desired distillation range is madepossible.

One aspect oi.' the invention is concerned with certain novelimprovements in the treatment of hydrocarbon vapors'to render thehydrocarbons chemically stable and this phase of the inventioncontemplates a process in which cracked distillate is brought intocontact with the heat of vapors evolved in the distillation oi crackedresidue to thereby vaporize the cracked distillate and the resultantvapors then subjected to puriiying or stabilizing treatment, such as bycontacting them with suitable catalytic material.'

When it is sought to purify or stabilize the light products from apressure cracking still by passing the vapors, before finalcondensation, through a mass of fullers earth or other similar adsorbenttreating material not only may the control and regulation of thecracking still` be made more difiicult but the product appears to' benot as satisfactory when treated in this way as it is when, the vaporfraction is first condensed and then subjected to the treatment with theadsorbent 'clay at a lower pressure. method of operation. however,involvesan in- 5 creased cost due-to the necessity of revaporizing thedistillate. In accordance with my invention hydrocarbon oil is subjectedto cracking and distillation to form a light distillate. such asgasoline or naphtha, which is collected as a condensate and a tar orresidue which is withdrawn from the cracking zone. This tar or residueis subjected to distillation by means of its contained heat at a lowerpressure than that obtaining in the cracking zone to thus vaporize outany gasoline or naphtha constituents that may be contained therein aswell as to recover therefrom constituents that are adapted for recyclingor retreatment for further cracking. The light distillate derived fromthe cracking operation is brought into contact with vapors evolved inthe distillation of the cracked residue to thus vaporize the distillate,and the resultant vapors including the vaporized cracked distillate andlight constituents derived from the distillation of 25 the residue aretreated with a solid adsorbent catalytic material such as fullers earthor the like.

I have found that in the vaporization of the residue byauto-distillation there is frequently sufficient heat to eifect avaporization of the total gasoline-or naphtha distillate derived fromthe cracking system in which such cracked residue was produced. Thus theinvention may be applied to a single cracking still or battery ofcracking stills or it may be applied to any convenient number ofcracking stills. In accordance with the invention tar or residue may bewithdrawn from a plurality of cracking stills or batteries thereof intoa common distilling or vaporizing chamber for distillation at reducedpressure by means of the contained heat in the residues and the gasolineor naphtha distillates or condensates obtained from these crackingstills or batteries may be brought into contact with vapors evolved inthe auto-distillation of the residues to thus vaporize the distillatesand the resultant vapor product, including constituents of desiredboiling point that have been vaporized out of the cracked residues andthe vaporized pressure 5o distillates, are subjected to treatment withadsorbent catalytic material such as fullers earth and the like toeffect polymerization of unstable constituents.

In order to more fully disclose the invention reference will now be hadto the accompanying drawing which illustratesschematically a preferredapparatus adapted for the practice of the invention.

In the apparatus thus illustrated a cracking 50 system including aheating coil I0 mounted in a furnace Il and a still or cracking chamberI2 adapted to receive the heated oil from the coil l0 is shown. 'Ihe oilto be treated which may be gas oil, or residual oil, or any of thepetro- 65leum stocks suitable for cracking, is drawn from -a suitablesource by a pump I3 which operates to charge the oil through the coil I0and thence after heating to the still l2. Any suitable temperature andpressure conditions adapted for 70 cracking may be employed in either orboth the coil I0 and still or reaction chamber l2.

The still |2 is shown in vapor communication with a dephlegmator orfractionating tower I4 adapted for separating out as a vapor the gaso-75 line or light distillate desired, which is passed to The latter v acondenser coili5 for condensation. and a liquid fraction which collectsin the bottom of the tower and may be removed by a pump "through line |1and charged through line I5 to the coil i0. In the operation of thetower I4 cooling may be supplied to the tower in order to regulate theend point of the vapor fraction taken oit to the condenser I5. Thecondensate obtained in the coil I5 is collected in a receiving drum Iland this condensate constitutes the gasoline or light distillate that itmay be desired to purify or stabilize. l*

Tar or residue formed in the still I2 is withdrawn through aline 2 0which extends to a tar or residue header 2| to which may be connectedother residue lines, such as 22 and 22. which may extend to otherbatteries of cracking stills (not shown). The residue thus dischargedinto the line 2| is passed through a pressure reducing valve 24 andthence into a tank 25 which preferably constitutes -a surge drum orcushioning drum to absorb the shocks or diil'erences in pressure thatmay occur due to the drawing of tar by shots from the different pressurebatteries to which the line 2| may be connected and so as to thusdeliver a more or less constant stream of residual oil through a line 28to a distilling chamber 21. It is preferable to reduce so far aspossible variations in pressure in the distilling chamber 21 in orderthat the end point of the distillate obtained from the strippingapparatus may be constantly kept maintained at the point desired andthus it is desirable to either draw tar or residue continuously from thepressure batteries or to provide some such cushioning device as thechamber 25. It may be pointed out that by having a considerable numberof batteries, such for example as l0 or 15, connected up to a singleresidue stripping unit, that by properly timing the withdrawal of liquidfrom the several batteries the influx of material into the strippingapparatus may be kept at a fairly constant rate so as to insure fairlyconstant distilling conditions.

The vaporizing chamber 21 may be of any suitable form and is shownprovided with a vapor line 28, a residue draw-off line 29 and a sectionof contact material 30 which may be adapted to prevent tarry or mistparticles from passing into the vapor line. If desired steam may beintroduced to aid vapor-ization in the still 21, although ordinarily theheat contained in the residue will b found ample. The still 21 may be'operated at pressures approximating atmospheric, although moderatesuperatmospheric pressures of for example 25 or 50 pounds may be used toadvantage. 'I'here appears to be no particular advantage in operatingthe still under a subatmospheric pressure.

The fractionating tower 3| shown is provided with a partitioning wall 32which divides the tower into an upper and lower section. The vapor line28 is shown discharging into the lower part of the upper section and aplurality of bubble trays 33 or other suitable contact material areindicated for the fractionation of the vapors. The lower section of thetower constitutes a stripping section and a line 34 having valved branchlines 35 extending to certain of the trays in the upper section isadapted for withdrawing liquid from these trays and delivering it intothe lower section of the tower. Trays 36 or other suitable contactmaterial and means 31 for introducing steam are shown in the lowersection of the tower. A vapor line 38 operates aorasoa 42 is providedfor introducing cracked distillateto be vaporized in the tower 3|. 'I'heline 4| is shown as extending to a pump 43 having an inlet line 44extending to the receiving drum I9 and provided with branch lines 46 and41 which extend'to the receiving drums of other pressure I batteries orto other sources of unstable .distillate (not shown). If desired, thevarious distillates from the several receiving drums may be conducted toa single storage tank and the pump 43 arranged to take suction on thistank.

The liquid that is introduced by the pump 43 to the fractionating tower3| serves as a cooling reflux forv the vapors and this liquid may bepartially or wholly vaporized in the tower by reason of the contact withthe hot vapors rising through the tower. Thus if the distillateintroduced from the line 4| is of the end point desired for the finalproduct it may be substantially wholly vaporized in the tower, or if thedistillate be of a higher end point itmay be vaporized in the tower tothe extent desired to obtain an overhead vapor product of desired endpoint while the higher boiling constituents may de-v scend through thetower to be removed as condensate therefrom. When introducing to thetower 3| distillate from the line 4| having a higher end point than thatdesired for the overhead vapor fraction it is advantageous to introducethe distillate or reflux at anintermediate point in the tower whereinthe end point of the liquid on the tray may approximate that of suchreflux, and when operating in this manner additional reux, such forexample as distillate from the receiving drum 58, or other liquid havingapproximately the same end point or composition as that of the vaporfraction being taken off the top of the tower 3|, may advantageously beintroduced to the top tray of the tower. When the reflux introduced tothe tower has the same end point as that of the desired vapor fractionit may advantageously be admitted to the top tray.

the distillate employed as reflux before introducing it into the tower3|. Thus when the production of naphtha from a given cracking unit or agiven number of such units is of such proportion to the vapors evolvedin stripping the residue from such cracking unit or units as not toallow the desired vaporization of the distillate by means of thesevapors it is of advantage to preheat the distillate before introducingit to the tower 3| thereby lessening the heat required for vaporizationof a given quantity of distillate and permitting -a greater amount ofdistillate to be used as reflux for a given amount of vapor evolved inthe residue stripping tower 21. By preheating the distillate to be usedas reflux it is possible to utilize more distillate from extraneoussources which it mai1 be desired to use as reflux. This preheating maybe used to advantage in cases, for example, where the end point of thedistil-- late used as reiiux is higher than that of the vapor fractiondesired. By providing the line 4| with branch lines extending to asuitable heating coil which may for example be lpositioned, in the Insome cases it may be desirable to preheat k 3 tower |4V to eilect heat.exchange with v.vapors therein or maybe arranged inheat .exchange withthe hot residue, as withdrawn through line4 29, a portion or all ofthedistillate used as reflux may be preheated tower 3|.A

beforeintroduction into the.

The vapors from the tower 3| which comprise the vaporized crackeddistillate that has been introduced thereto as reflux together withconstituents of desired boiling point distilledfout of the crackedresiduemay be passed directly to a condenser but in the apparatus shownin the drawing a vapor line-46 is indicatedl for directing the vaporsinto a treatingchamber 49 which contains a bed of solid adsorbentcatalytic material 50, Asuch as fullers earth or clay adapted foreffecting a polymerization of unsaturated or unstable constituents inthe vapors. 'I'he resultant polymers or liquid product thus obtainedcollects in the bottom of the chamber 49 and I'he vapors leave the tower49 through a vapor line 55 by which they are conducted to a scrubbing orfractionating tower 56 which may serve as a mist extractor, as well as afractionating device more particularly in the earlier parts of the runwhen the end point of the vapors may run higher than that desired. Thevapors pass to a condenser coil 51 wherein they are condensed and thecondensate is collected in a receiving drum 58. A pump 59 is shownhaving a line 60 taking suction on the receiving drum 56 and a dischargeline 6| extending to the tower 56 so that whenever desired liquid fromthe receiver 58 may be employed as -a reflux for .this tower. A backtrapor reflux line 62 isshown for reuxing to the bottom of the chamber 49liquid collected in the lower part of the tower 56.

One method of operation contemplated by the invention is to maintain theresidue stripping still 36 under avacuum which may advantageously beaccomplished by the use of a vacuum pump in connection with thereceiving drum 56, the pump being preferably arranged to take suction ona gas line extending from the receiving drum, and a pump may also beused in the line 29 for withdrawing residue from the still 21. In thismethod of operation the treating of the vapors by the contact material56 is carried on under avacuum. In another method of operation thepressure tar or residue is distilled in a two stage operation by beingfirst distilled at atmospheric pressure or at a relatively lowsuperatmospheric pressure and the residue from this distilling operationconducted to a secondary still which is maintained. under a vacuumwherein the final distillation takes place. In this method of operationthe lighter constituents will come off in the primary distillation andthe fractionation of these vapors and the treatment of the light vaporfraction by the catalytic contact material may take place under thepressure at which the primary distilling operation is conducted.

The final product as obtained in the receiving drum 58 may be passed toa' rectifying tower for rectification whenever necessary or desirable inorder to produce a product of desired vapor tension or, if desired, thedistillate collected in the line 44 may be subjected to rectificationbefore being introduced to the tower 3|.

Although the preferred embodiment of the invention has been set forth inconnection with apparatus having a particular construction andarrangement of parts and modelo! operation. it is obvious that variouschanges andmodiiications may be made thereinrwhilesecuring to a greateror less extent some or. all of the bene'ts of thev 10 yl. 'Ihe processo! `treating hydrocarbon oil which comprises subjecting said oil tocracking temperature under superatmospheric pressure to cause conversionthereof into lighter products, separating the resulting hot crackedproducts into l5 a distillate of a given end point higher than thatdesired for the nnal product and a hot residue, vaporizing said residueby .reducing the pressure thereon, redistilling said distillate bythermal contact with the vapors derived from the vaporized 20 residue,fractionating the combined vapors to separate vapors of the desired endpoint, and treating said vapors last mentioned, while still hot, withsolid adsorbent catalytic material to effect polymerization oi.'unstable constituents and amm' form a desired product free from saiddistillate iirst mentioned.-

:2. A process according to claim. 1 wherein polymers condensed' by.treatment of the said vapors last mentioned 'are used as reilux in theIractionating of said combined vapors. f

3. The process of treating hydrocarbon oil which comprisessubjectingsaid oil to cracking temperaturerunder superatmospheric pressure tocause conversion thereof into lighter products, separating the resultinghot cracked products into a distillate of a given end point and a hot

